Cellular radio and telephone systems are in wide use and, in these systems, a mobile receiver operates through a plurality of cells, usually three, located in the area of the receiver. In the communication process, each cell or cell site generates a particular carrier signal or supervisory audio tone (SAT) having a specific frequency. These supervisory tones, from the three or more cell sites, are FM modulated with voice signals on each channel.
In the operation of these cellular systems, the cell sites are monitored to measure the frequency and power of the supervisory tones in order to insure that true carrier (SAT) frequencies are generated since proper operation of the receivers requires such exact signal frequencies.
Apparatus for monitoring the supervisory tones in a cellular system is available, however, such available apparatus is slow in operation and this is undesirable for use in a situation where a large number of frequency measurements are to be made.